A 29-year-old bird collector presents to the local clinic with what he describes as flu-like symptoms. He doesn’t look ill, and has a slight fever, headache, and a dry hacking cough. He denies the production of sputum or hemoptysis. There are no crackles heard on auscultation, and a radiograph shows small streaks of infiltrate. It is determined that he has pneumonia. What is the most likely organism causing his disease

**Core Concept**
Pneumonia is an inflammatory condition of the lung primarily caused by infection, with various pathogens responsible for its development. The clinical presentation and radiographic findings aid in narrowing down the likely causative organism.

**Why the Correct Answer is Right**
The patient's presentation of a dry hacking cough, slight fever, and small streaks of infiltrate on the radiograph is suggestive of adenoviral pneumonia. Adenoviruses are a common cause of community-acquired pneumonia, particularly in individuals with underlying conditions such as asthma or those exposed to birds, like the patient in this scenario. Adenoviral pneumonia often presents with mild symptoms and a dry cough, which aligns with the patient's description.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be tempting, but Mycoplasma pneumoniae is more commonly associated with atypical pneumonia, particularly in young adults, and often presents with a more severe cough and systemic symptoms.

**Option B:** Chlamydophila pneumoniae is another atypical pathogen that can cause pneumonia, but it typically affects older adults and those with underlying conditions, and often presents with a more severe disease course.

**Option C:** Streptococcus pneumoniae is a common cause of community-acquired pneumonia, but it typically presents with more severe symptoms, such as high fever, productive cough, and systemic illness.

**Option D:** Influenza virus can cause pneumonia, but it typically presents with more severe symptoms, such as high fever, cough, and systemic illness, and often affects older adults or those with underlying conditions.

**Clinical Pearl / High-Yield Fact**
Remember that adenoviral pneumonia can be challenging to diagnose, and a high index of suspicion is necessary, particularly in patients with a history of exposure to birds or other animals.

**Correct Answer: A. Adenovirus.**

✓ Correct Answer: C. Chlamydophila psittaci